A channel in a wireless local area network (WLAN) is an exclusive channel. When one terminal (Station, STA) communicates with an access point (AP), a wireless channel is occupied. During such a process, another STA has to wait. 802.11 allows a STA to use an RTS frame and a CTS frame to clear a transmit area, that is, before data is sent, the STA first instructs other STAs around not to send data at this moment. As shown in FIG. 1, when a device 1 sends data to a device 2 in a WLAN, the device 1 sends an RTS packet to the device 2. In this way, after receiving a RTS packet, none of other devices sends data within a specified period of time. After receiving a RTS packet, the device 2 sends one CTS packet again. In this way, it is ensured that none of the other devices sends data within a specified period of time. After exchange of RTS/CTS packets is completed, transmission of data starts between the device 1 and the device 2 (see step 3 in FIG. 1). After transmission of data is completed, the device 2 returns an ACK (see step 4 in FIG. 1). FIG. 2 shows a process of signaling exchange between the device 1 and the device 2. After RTS/CTS exchange between the device 1 and the device 2 is completed, transmission of data starts until the transmission is completed.
In the prior art, a case in which more than two WLAN APs form a network (a single-frequency WLAN for short) to operate may occur. In an example shown in FIG. 3, three WLAN APs, that is, AP1, AP2, and AP3, are distributed at a same point to form a single-frequency network, in which directional antennas are used, and each AP covers an area of 120 degrees. A STA is connected to an AP to perform a data service.
In the foregoing case, when sta1 inside a coverage area of AP1 performs data communication with AP1, sta2 (located inside a coverage area of AP2) and sta3 (located inside a coverage area of AP3) may also perform data communication with AP2 and AP3 respectively.
Because channels used for data communication are limited in a single-frequency WLAN with multiple APs, it is likely that AP1, AP2, and AP3 share a same channel when communicating respectively with STAs inside respective corresponding coverage areas. In this case, mutual interference is caused inside coverage areas of AP1, AP2, and AP3, and network performance is severely affected.